The present invention relates to the field of semiconductor wafer processing, and more specifically, to a multi position load lock chamber used in semiconductor wafer processing.
FIG. 1 is an isometric view of a piece of semiconductor manufacturing equipment (an epitaxial reactor 10). The epitaxial reactor 10 is partitioned into the wafer handling chamber 16, load locks 14 and 15, and a process chamber 20 that is isolated from the load locks 14 and 15 and the wafer handling chamber 16 by isolation gate valve 18.
In operation, cassettes of semiconductor wafers (not shown) are placed in the load locks 14 and 15 through load lock portals 32 and 34. After loading the wafer cassettes into the load locks 14 and 15, the load lock portals 32 and 34 are closed to isolate the wafers from the surrounding atmosphere. The load locks are purged by the purge gas that purges out oxygen, moisture and any undesirable particles that may have inadvertently entered the load locks 14 and 15 while the load lock portals 32 and 34 are opened to receive the wafer cassettes.
After completing the purge, the load locks 14 and 15 are opened to the wafer handling chamber by lowering the cassette in an elevator (not shown) which breaks an air tight seal. The wafers are then transported sequentially from the cassettes to the process chamber 20 by a transfer arm 29 that has, for example, a Bernoulli wand end effector 36.
Subsequent to the purging of the load locks 14 and 15 and wafer handling chamber 16, the isolation valve 18 is opened. The transfer arm 29 is used to move the wafers from the load lock 14 or 15 into the process chamber 20 for wafer processing. The transfer arm 29, including a low ingestion Bernoulli wand 36, is within the wafer handling chamber 16. In operation, the Bernoulli wand 36 picks up the semiconductor wafers one at a time from the cassettes (not shown) in one of the load locks 14 and 15. Each wafer is then transported through the open isolation gate valve 18 to a susceptor 38 within the process chamber 20.
After the processing of the wafer is completed, the isolation gate valve 18 is opened and the Bernoulli wand 36 picks up the wafer and returns it to the slot within the same cassette that the wafer was originally retrieved from.
Although the above system is very successful, there is always a desire by the semiconductor manufacturers to increase the throughput of their equipment. However, factory space comes at a premium so that the use of factory floor area for processing equipment must be maintained at a minimum. Additionally, the semiconductor manufacturers appreciate the advantage of performing both preprocessing and post processing operations on semiconductor wafers without affecting the throughput of the processing equipment or the footprint of the equipment on the factory floor.